The results of this study indicated that PTEN was highly expressed in MCF-7 and T-47D, classified as luminal-type breast cancer cell lines but expressed at low levels in the HER2-overexpressing subtype (SK-BR-3), TNBC (MDA-MB-231), and PTEN-deficient breast cancer (BT-549). This evidence concerns the gene ERBB2 and breast cancer.